World widely, a variety of fermentation methods using microorganisms have been used for mass-production of useful products such as amino acids, etc. In particular, many technologies including the development of bacterial strains and establishment of fermentation conditions have been developed for successful fermentation using microorganisms. To develop bacterial strains for mass-production of useful products, genetic factors directly or indirectly involved in the upstream of glycolytic pathway are properly used to develop a strain with a higher efficiency. A representative technique is global Transcription Machinery Engineering (gTME) which induces random mutations in recruiting proteins of RNA polymerase to regulate all genetic expressions in cells.
RNA polymerase used in a transcription step of a microorganism is a macromolecule consisting of 5 subunits; two alpha, beta, beta prime, and sigma subunits. Its holoenzyme is expressed as α2ββ′σ. Of them, a core enzyme (α2ββ′) is used in all transcription steps, excluding the step of transcription initiation. In microorganisms, transcription begins with the specific binding of RNA polymerase to a promoter, and the holoenzyme binds with DNA in the region about 45 base pairs upstream and about 10 base pairs downstream from the initiation point of RNA polymerization.
Beta prime subunit of RNA polymerase of E. coli has an evolutionarily highly conserved region of A˜H. Many studies have reported that induction of mutations in this region causes different changes such as weakening of binding of RNA polymerase with other factors, increase in growth temperature sensitivity of the strain, etc. However, there have been no studies about the application of gTME to a bacterial strain belonging to the genus Corynebacterium and changes in characteristics by mutations.
Genes encoding beta and beta prime subunits of the subunits constituting RNA polymerase of a bacterial strain belonging to the genus Corynebacterium, namely, rpoB and rpoC, form an operon, and they consist of nucleotides of 3.5 kb and 4.0 kb, respectively.
The present inventors introduced random mutations into rpoC, which is derived from the bacterial strain belonging to the genus Corynebacterium, and screened a mutant that contributes to the improvement of L-lysine productivity. They found that the introduction of mutations into the regions corresponding to G and H of E. coli-derived rpoC greatly improves lysine productivity, thereby completing the present application.